# _*_ coding: utf-8 _*_
import math
# pip install matplotlib 引入包
import matplotlib.pyplot as plt

if __name__ == '__main__':
    x = [float(i)/100.0 for i in range(1,300)]
    y = [math.log(i) for i in x]
    plt.plot(x,y,'r-',linewidth=3,label='log Curve')
    a = [x[20],x[175]]
    b = [y[20],y[175]]
    plt.plot(a,b,'g-',linewidth=2)
    plt.plot(a,b,'b*',markersize=15,alpha=0.75)#alpha=0.75透明的，markersize=15，标记大小为15
    plt.legend(loc='upper left')#显示图例，位置在左上角
    plt.grid(True)#显示网格
    plt.xlabel('x')
    plt.ylabel('log(x)')
    plt.show()